Technical Field
The present invention relates to flash memory, and in particular to methods for reprogramming data and apparatuses using the same.
Description of the Related Art
Flash memory devices typically include NOR flash devices and NAND flash devices. NOR flash devices are random access—a host accessing a NOR flash device can provide the device any address on its address pins and immediately retrieve data stored in that address on the device's data pins. NAND flash devices, on the other hand, are not random access but serial access. It is not possible to access any random address in the way described above for NOR—instead the host has to write into the device a sequence of bytes which identifies both the type of the requested command (e.g. read, write, erase, etc.) and the address to be used for that command. The address identifies a page (the smallest chunk of flash memory that can be written in a single operation) or a block (the smallest chunk of flash memory that can be erased in a single operation), and not a single byte or word. Memory cells of a flash memory may malfunction after being accessed numerous times. Particles or mask defects in manufacturing a flash memory may cause a whole wordline of a storage unit to fail. Accordingly, what is needed are methods for reprogramming data when the programming failure appears, and apparatuses using the methods.